On screen display graphics generators for analog televisions are well understood and are widely used. Almost every analog television sold has the capability to overlay informational displays on top of the received video. Additionally, accessory devices such as VCR's, cable set top boxes, and satellite set top boxes can overlay display information on top of a received or locally generated video signal.
Digital televisions, however, are intended to receive and process digital television signals. Such digital television signals are in the form of MPEG-2 encoded digital video transport streams (see ISO/IEC 13818-1 and ISO/IEC 13818-2). MPEG-2 encoded digital video transport streams may also be received by a digital accessory device from digital satellites, digital cable broadcast systems, or terrestrial digital broadcast systems, or may be produced by an accessory DVD player or digital VCR. The digital stream received by a digital accessory device is then fed to a digital television receiver. If the accessory device is to create informational displays to be overlaid or otherwise mixed with the original MPEG-2 encoded video, and then send that video plus the display information as an MPEG-2 encoded transport stream to a digital television, new techniques of overlaying on-screen displays on video are required. The present invention is directed to such new techniques.